Concert-goers sit on the roof of a Volkswagen bus at the Woodstock Music and Arts Fair at Bethel, N.Y., in mid-August 1969. The three-day concert attracted hundreds of thousands of people, and became a landmark cultural event of the late '60s. USATODAY / file photo

The crowd at the Woodstock festival in Bethel, New York, in August 1969. AFP/Getty Images / file photo

In this August 1969 file photo, a couple hugs during the Woodstock Music and Art Festival in Bethel, N.Y. Associated Press / file photo

DO NOT USE THIS PHOTO, IT'S OUT OF OUR PLAN AND WE HAVE TO PAY FOR IT. Concert goers surround the stage as Joe Cocker performs at the Woodstock Music and Arts Festival in Bethel, N.Y. on Aug. 17, 1969. Associated Press / file photo

In this August 16, 1969 file aerial photo, music fans at the original Woodstock Music and Arts Festival are packed around the stage, at bottom, in Bethel, N.Y. Archaeologists from New York's Binghamton University are trying to find the exact location of the stage and say aerial shots taken nearly 50 years ago can't be relied upon to help them, because the hillside was re-graded in the late and the spot of the original stage is under a layer of fill. Associated Press / file photo